Adjustable pitch propeller



Sept. 10, 1935. UIRES 1 2,013,930

ADJUSTABLE PITCH PROPELLER Filed Sept. 23, 1951 3 Sheets-Sheet 1 lIl-l-l-l-l-l-lll INVENTOR J'ohn Sal/bras.

ATTORNEYS Sept. 10, 1935.

Filed Sept. 23, 1951 3 Sheets-Sheet 2 3 6 /7\ J ii 35 3 40 39 J A J I ,i 57 {I 5 5 I. II 3, 00

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INVENTOR I J'o br/ Sol/ares.

A ORNEYS- Sept. 10, 1935. J. SQUIRES 2,013,930

ADJUSTABLE PITCH PROPELLER Filed Sept. 23, 1931 3 Sheets-Sheet 3 INVENTQR Job 77 5471/: res.

ATTORNEYS Patented Sept. 10, 1935 v UNITED STATES PATENT OFFICE This invention relates to an improved aircraft propeller of the type which has blades that are adjustable in pitch and particularly to improved mechanism which is responsive to the speed ofrotation of the propeller for automatically varying the pitch of the blades during flight.

Propellers having blades whi h are adjustable in pitch generally include a hub having opposite sockets in which cylindrical end portions of the blades are journaled. Rotatably mounted propeller blades normally tend to turn about their axes toward positions of increased pitch under the action of wind pressure, and toward positions of zero pitch under the influence of centrifugal action upon the mass of the blades. The centrifugal pitch reducing action, which results from the tendency of the center of mass of the blade to swing into the'plane of rotation of the propeller, exceeds the aerodynamic pitch increasing action of the wind pressure and therefore the blades are urged toward a zero pitch position by the resultant of these opposed forces.

The amplitude of the turning efi'ect of the cen- I self-adjusting propeller which embodies the intrifugal action upon the mass of the bladesand the amplitude of theopposed aerodynamic in-'- fluence for predetermined rates of rotation of the propeller and pitch of the blades can be accurately determined by calculation or by experimentation. In this manner the forces required to hold the blades in selected positions during take off and flight, respectively, may be ascertained. By opposing the turning effects which are exerted upon the blades, in part by means which are re-;

sponsive to the rate of rotation of the propeller,

the pitch of the blades may be automatically changed so as to condition the propeller for both take off and flight. Since aircraft propellers rotate more freely and at -a higher rate when the aircraft is in forward motion than when it' is i 0 at rest, centrifugal action may be relied upon to automatically effect the change in the pitch of the blades as the propeller speeds up following take off of an aircraft. a

The main objects of the invention are to pro- 45 vide means for automatically predetermining the pitch of rotatably adjustable propeller blades; to provide means of this kind which is responsive to the-rate of rotation of a propeller; to provide means for yieldably holding the blades in mini- 50 mum pitch positions during take off and ascent of an aircraft, to provide suitably located counterweights on the propeller blades for building up centrifugal moments, in opposition to the pitch reducing turning efiect exerted on the blades,

55 which exceed the latter turning effect at predeter- -line ll-ll of Figure S.

mined rates of rotation of the propeller so as to increase the pitch of the blade during flight; and to provide propeller blades that have thickened walls at selected portions which serve as counterweights in developing. centrifugal moments for 5 rotating the blades against the inherent turning efiect exerted thereon during operation ofthe propeller at predetermined speeds.

Further objects of the invention are to provide propellerbladeregulating apparatus which retains 10 the blades at a pitch that permits the engine by which the propeller is driven to run substantially at its full power rate of operation while an aircraft is at rest; andto provide apparatus of this character which automatically increases the pitch of 15 the blades as the loadupon the propeller is decreased by forward movement of the aircraft so as to both condition the propeller for level flight and to maintain uniform engine operation at a substantially full power rate. v

An illustrative embodiment of the invention-1s shown in the accompanying drawings in which:

Figure 1 is a fragmentaryv side elevation of a v vention. 25 Figure 2 is an enlarged horizontal section taken on the line 22 of Figure 1. Figure 3 is an end elevation showingthe propeller partly in section.

Figure 4 is a horizontal section taken onthe 30 line44 ofFigure2.-

Figure 5 is a central vertical. section taken on I the line 5-5 of Figure 4.

Figure 6 is a horizontal section taken on the line 6-6 of Figure 1;- v

Figure '7 is an end,elevation' similar to-Figure 3, but showing a propeller which embodies a modifled form of the invention, one of the blades of the propeller, being illustrated partly in section.

Figure 8 is aside elevation of a propeller blade of the type used in the form of the propeller shown in Figure 7; i

Figure 9 is a horizontal section taken on the line 9-9 of Figure 8. 1

Figure 10 is a, horizontal section taken on'the line lli- -lli of Figure 8. 1

Figure 11 is a horizontal section taken-on the In the form shown, my improved propeller I has a hub which includes a cylindrical casing:

formed of two semi-cylindrical sections. These sections arecl'amped together by bolts 3 which extend through apertured bosses! on the outer' periphery of the section, as illustrated in Figure 1. The respectively opposite ends ofthe casing 2 have inwardly extending flanges 6 and 6. Formed in the interior of the casing 2, in spaced .relation to each end flange and 6, are seats 1 sponding bearing seats l5 and IE on the flanges II and I2 of the propeller blades. Located between the bearing seats I 3 and I5 at one end of the hub and between the bearing seats I 4 and I6 at the other end of the hub, are ball bearings l'l and I8 which are held apart by cages I 9 and 20,

respectively. These'ball bearings hold the propeller blades in spaced relation to the surrounding structure of the hub permitting free rotation of the blades and minimizing frictional resistance.

In practice, adjustable propeller blades of this type are held at an inclination to the plane of rotation of the propeller during operation so as to produce a pitch that is suitable for impelling an aircraft forwardly. The pitch at which a blade is positioned causes the center of mass of the blade to be placed to one side or the other of the plane of rotation. During operation of the propeller at the rate at which it is normally rotated the centrifugal action upon the blade tends to move its center of mass into the plane of rotation thereby urging the blade toward a neutral or zero pitchposition. This influence is opposed by the aerodynamic forces that tend to increase the pitch of the blades and which are lower in amplitude than the centrifugal forces.

The action of the forces to which the blades of a propeller embodying my invention are subjected is illustrated in Fig. 7 in which the numeral 60 designates the center of the base portion of a blade which is revolved, during operation, about an axis 6| in the direction of the arrow 62. The wind pressure acts upon the blade in the direction of the arrow 63 thereby urging the blade toward an increased pitch position. The center of mass of the blade 'indicated at 64 tends to move into the plane of rotation of the propeller, which plane is designated by the line 86. The force tending (to turn the blades into the plane of rotation due to the centrifugal action greatly exceeds the force tending to turn the 'blades to greater pitch due to wind pressure.

The automatic blade adjusting apparatus, shown in the drawings, includes means for positively holding the blades against rotation to a position below a predetermined minimum pitch.

This apparatus also includes a resilient member which, like the centrifugal'moments of the mass, of the blade, urges the latter toward a neutral pitch position and yleldably holds the blades against movement from the minimum pitch position. Mounted on the sides of the blades 9 and III are counterweights 2| and 22; respectively, which, during rotation of the propeller at. a predetermined rate, turn the blades toward increased pitch positions; against the turning efiects of the resilient member and the resultant of the other forces.

In the form shown in Figures l to 6 inclusive, the hub I is provided with a centrally located and internally splined sleeve 23 for receiving a propeller shaft 24 which extends outwardly through a plate 25 on the nose structure 26 of an engine.

Slidably mounted on the sleeve 23 is a concentric collar 21 which has an internal flange 28 extending into a recess 29 in the outer periphery of the sleeve 23. The flange 28 is normally held against a shoulder 30 on the sleeve 23 by a coil spring 3| 6 which bears at one end upon the flange '28 and at its other end against the opposite end wall 32 of the recess 29 so as to yleldably hold the collar 21 against inward movement.

Mounted on the internal side of the hub casing 2 of the propeller is a bracket 33 having a bear-' ing 34 in which a pin 35 is journaled. A lever 36 is rigidly fixed at its intermediate portion to the outer end of the pin 35, as shown in Figure 5. This lever has a rounded outer end portion 31 which is received in a slot 38 in the flange H of the blade 9. Integrally formed on the inner end of the lever 36 is a cylindrical boss or nib 39 which is received in an aperture 40 formed in the shiftable collar 21. The lower blade H), as viewed in Figure 5, is provided with a similar lever 4| having a pin 42 which is journaled in a bearing 43 of a bracket 44 that is secured to the opposite side of the hub casing 2. The lever 4| has a rounded outer end 45 which is received in a recess 46 of the flange |2 of the blade l0. Provided on the inner end of the lever 4| is a cylindrical boss 41 which is received in a recess 48 of the collar 21 and located diametrically opposite from the boss 39 of thelever 36.

In operation, the spring 3| yleldably holds the collar 21 and the inner ends of the levers .36 and 4| against inward movement toward the engine 26, thereby yleldably holding the blade 9 against counter-clockwise rotation to an increased pitch position. The blade i0 is likewise yieidably held against clockwise rotation to an increased pitch position. The shoulder 30 of the sleeve 23 positively limits outward movement of the collar 21 and inner ends of the levers 36 and 4| so as to predeterminethe minimum pitch positions of the blades.

The blades 9 and I0 are held against rotation from their minimum pitch positions by the ,"couple resulting fromthe opposed turning effects of the wind pressure and centrifugal moment of the blades which can be determined by calculation or experimentation; and by the force of the spring 3| which may be predetermined. Hence, the blades are held in their low pitch positions 50 by known forces which must be overcome in order to increase the pitch of the blades.

' The weights 2| and 22 which are located on the same side of the plane of rotation of the propeller as the leading edges of the blades thereof are relied upon to increase the pitch of the blade against the resultant force'of the aerodynamic and centrifugal moments, and against the action of the spring 3| when the propeller exceeds a predetermined rate of rotation. By properly proportioning the amplitude of the weights with respect to the compression of the spring 3| and the other forces acting upon the blades, the change in the pitch of the blades may be caused to occur at any selected rate of rotation of the propeller.

In practice, it is advantageous to have the blades set at a minimum pitch during operation of the propeller while the air craft is at rest, which may permit the engine to come up to within approximately two per cent, to three per cent of its full power rate of operation. With the, present invention the counter balance aerodynamic moments acting upon the blades and to substantially balance the initial compressive force of the spring when. the propeller is driven by an engine operated at its rated speed and full load and while the air craft is at rest on the ground. Under. these conditions the blades are held at their minimum pitch positions, for instance ten degrees, by the residual force in the springs which, under such conditions, will be quickly overcome by the weights upon a slight increase in engine speed as will occur upon forward movement of the air craft. When the aircraft moves forwardly, the propeller and the engine tend to increase their rate of rotation, causing the mass of the counter weights 2| and 22 to automatically turn the blades toward increased pitch positions. The increased pitch of the blades which is more suitable for flight than the minimum pitch thereof, places the propeller under a greater load thereby governing the rate of operation of the propeller so as to maintain substantially uniform rotation of the engine at approximately its full power operating speed.

When the rate of rotation of the propeller decreases the centrifugal eifects of the counter weights also decrease and the blades are automatically turned toward their minimum pitch positions by the spring 3| and the resultant force of the aerodynamic and centrifugal moments. In this manner a minimum pitch is maintained up to a predetermined rate of rotation of the propeller and during rotation of the latter above this predetermined rate, the pitch is proportioned with respect to the rate of operation of the propeller.

The hub and automatic blade regulating apparatus employed in the form of my invention, illustrated in Figures '7 to 11, inclusive, are substantially identical to the corresponding $171110!- tures shown in Figures 1 to 6, and their parts are accordingly designated by the same numerals. The blades 49 of the propeller, shown in detail in Figures 8 to 11 inclusive, diifer from the blades shown in Figures 1 to 6, inclusive, in that they have eccentric inner andouter peripheries. This construction provides a thickened wall 50, shown in Figs. 7, 9 and 10, on one side of the blade which is located on the same side of the plane of rotation of the propeller as the leading edge of the blade, and which serves as a counter balance weight for opposing and overpowering the turning effects upon the blade of the spring 3| and other forces at a predetermined rate of rotation of the propeller. The thickened wall 50 preferably extends throughout the entire length of the blade and it obviates the use of additional counter weights. The operation of the propeller, shown in Figures '7 to 11, inclusive, is substantially the same in all respects as that set forth in the discussion of the form of the invention shown in Figures 1 'to 6 inclusive.

Although but severalembodiments of this invention have been herein shown and described, it will be understood that numerous details of the construction shown. may be altered or omitted without departing from the spirit of this invention as defined by the following claims.

I claim:

1. A propeller including a hub, a blade rotatably mounted in said hub, means for positively holding said blade against turning to 'a position below a predetermined pitch, a yieldable member for holding said blade against turning to a position above said predetermined pitch, and a counter weight mounted on the side wall of said blade and so constructed and arranged as to create a centrifugalmoment in opposition to said yieldable holding member and to turn said blade to an increased pitch position during full speed opera- 5 tion of said propeller.

2. A propeller including a hub, a blade rotatably mounted in said hub, means for holding said blade against rotation to a position below a predetermined minimum pitch, said blade having a center of mass located on one side of the plane of rotation of the axis thereof normally tending to rotate said blade toward a neutral pitch position, and a counter weight ilxed on the side wall of said blade and so constructed and arranged 15 with respect to said plane of rotation as to turn said blade against said normal turning tendency to a position of increased pitch during operation of said propeller at a predetermined rate.

3. A propeller including ahub, a bladerotatably mounted in said hub, means for holding said. blade against rotation to a position below a predetermined minimum pitch, said blade having a center of mass located on one side of the plane of rotation of the axis thereof normally tending to rotate said blade toward a neutral pitch position,

a counter weight fixed on the side wall of said blade and so constructed and arranged with respect tosaid plane of rotation as to turn said blade against said normal turning tendency to a position of increased pitch during operation of said propeller at a predetermined rate, and a re-.

, silient member for predetermining the maximum pitch position of said blade and the rate of operation ofsaid propeller required to place said blade in said maximum pitch position.

4. A propeller including a hub, a hollow blade rotatably mounted on said hub including a weighted side wall and having its center of mass on one side of the plane of rotation of the propeller for urging said blade toward an increased pitch position during rotation of said propeller, and a resilient member for predetermining the maximum pitch position 01 said blade and the rate of operation of said propeller required to place said blade in said maximum pitch position.

5. A propeller including a hub, a hollow blade rotatably mounted on said hub including a weighted side wall portion and having a greater mass on the side of the plane of rotation of said propeller on which the leading edge thereof is located than on the opposite side of said plane for urging said blade toward an increased pitch position during rotation of said propeller, and a resilient member for predetermining the maximum pitch position of said blade and the rate of operation of said propeller required to place said blade in said maximum pitch position.

6. A propeller including a hub, a hollow blade rotatably mounted on said hub including a weighted side wall portion and having a greater mass on the side of the plane of rotation of said propeller on which the leading edge thereof is located than on the opposite side of said plane for urging said blade toward an increased pitch position during 05 rotation of said propeller, means for positively holding said blade against rotation to a position below a predetermined pitch, and a resilient member for predetermining the maximum pitch posi- 1 tion of said blade and the rate of operation of said "0 propeller required to place said blade in said maximum pitch position.

'7. A propeller including a hub, a hollow blade rotatably mounted in said hub having a thickened wall located on the same side of the plane 75 rotatably mounted in said hub normally tending to turn toward a neutral pitch position under the influence of the resultantforce of the wind pressure and the centrifugal action of its mass during operation of said propeller, and means for positively holding said blade against rotation to a position below a minimum pitch, said blade having-a weighted thickened side wall portion for turning the latter to a maximum pitch position against the influence of said resultant face when said propeller is operated at a predetermined rate.

9. A propeller including a hub, a blade rotatably mounted in said hubnormally tending to turn toward a neutral pitch position under the influence of the resultant force of the wind pressure and the centrifugal action of its mass during operation of said propeller, means for positively holding said blade against rotation to a position below a minimum pitch, a weight fixed on the side wall of said blade and so constructed and arranged as to turn the latter to a maximum pitch position against the influence of said resultant force when said propeller is operated at a predetermined rate, and a resilient member for acting in opposition to said weight for predetermining the maximum pitch of said blade.

10.- A propeller including a hub, a hollow blade journaled in said hub normally tending to turn toward a neutral pitch position during operation of said blade, and means for holding said blade against rotation to a position below a predetermined pitch and including a resilient member for yieldably holding said blade against rotation above said predetermined pitch, said blade having a thickened wall on one side thereof for opposing its normal tendency to turn toward a neutral pitch position and adapted to regulate the pitch of said blade in proportion to the rate of operation of said propeller when the latter is rotated above a predetermined rate.

11. A propeller including a hub, a tubular hollow blade rotatably mounted on said hub including a thickened side wall and having a greater mass on one side of its plane of rotation than on the other side thereof for normally urging said blade toward increased pitch positions during rotation of said propeller, means for holding said blade againstrotation to a position below a minimum pitch, and resilient means for yieldably opposing rotation of said blade toward increased pitch positions and adapted to proportion the pitch of said blade with respect to the rate ofrotation of said propeller.

12. In an aircraft having an engine, a propeller operable by said engine including a hub, a hollow blade rotatably mounted on said hub having a thickenedwall on the same side of the plane of rotation of said-propeller as the leadingedge of said blade for urging the latter toward an increased pitch position, means for holding. said blade against rotationto a position below a predetermined pitch including a resilient member for yieldably holding said blade against rotation above said predetermined pitch during operation of saidengine and propeller while said aircraft is at rest on the ground, the centrifugal action upon said thickened side of said blade being adapted to turn the latter against the action of said resilient member to a higher pitch position when said'propeller is operated at a faster rate during forward movement of said aircraft.

13. In an aircraft having an engine, a propeller operable by said engine including a hub, a hollow metal 'blade rotatably mounted on said hub, and means for holding said blade against 10 rotation to a position below a predetermined pitch including a resilient member for yieldably holding said blade against rotation above said predetermined pitch during operation of said engine and propeller while said aircraft is at rest on the ground, the wall of said blade being provided with a greater thickness of metal at a selected portion thereof than at its-remaining portion for creating a tortional centrifugal action so as to turn the latter against the action of said resilient member to a higher pitch position when said propeller is operated at a faster rate during forward movement of said aircraft. v

14. A propeller including a hub, a blade rotatably mounted on said hub normally tending to turn toward a neutral pitch position during operation of said propeller, and a counter weight fixed on the side wall of said blade and so constructed and arranged as to overpower the pitch reducing turning efiect thereon during rotation of said propeller at a predetermined rate.

15. In an aircraft having an engine, a propeller operable by said engine including a hub, a hollow metal blade rotatably mounted on said hub, the wall of said blade being provided with a greater thickness of metal at a portion thereof on one side of the plane of rotation of said propeller than on its other side for urging said blade toward positions of increased pitch, and means for yieldably holding said blade in a low pitch position 40 while said engine is operated at substantially full power and said propeller at substantially full load, said blade being rotatable against the action of said means under the centrifugal action upon the portion thereof having a greater thickness of metal when the load on said propeller decreases, so as to increase the pitch of said blade for maintaining uniform operation of said engine.

16. In an aircraft including an engine having a propeller shaft, a propeller-having a hub fixed on said shaft, a blade rotatably mounted on said hub normally tending to turn toward its minimum pitch position during operation of said propeller, means including a resilient member for urging said blade toward its minimum pitch position, and a counter weight fixed on the side wall of said blade having sufllcient mass and so constructed and arranged as to balance the normal tendency of said blade to turn toward its minimum pitch position and to balance all but a small residual of the influence of said resilient member when said propeller is operated at the full rated speed and under full load of said engine so as to enable the unbalanced residual force of said resilient member to be overcome quickly by the centrifugal weights upon a slight increase of the engine speed resulting from forward movement of the aircraft.

17. A propeller including a hub and a hollow blade rotatably mounted in-said hub having a thickened wall portion located on one side of the plane of rotation of said blade and so constructed and arranged that it urges said blade toward an increased pitch' position during operation of said propeller.

18. A propeller including a hub, a hollow blade rotatably mounted in said hub having a thickened wall portionlocated on one side of the plane of rotation of said blade and so constructed and arranged that it urges said blade toward an increased pitch position during operation of said propeller, and means for opposing rotation of said lade to an advanced pitch position.

19. A propeller including a hub structure having a propeller shaft receiving sleeve disposed therein, an adjustable blade member rotatably mounted on said hub structure and so constructed and arranged as to normally tend to turn toward an increased pitch position during operation of said propeller, a collar confined within said hub structure and shiftably mounted on said sleeve, means for articulating the shifting movement of said collar and the rotative movement of said blade, and a resilient member bearing between said collar and said hub structure for yieldably urging said blade toward a decreased pitch position.

20. A propeller including a hub structure having a propeller shaft receiving 'sleeve disposed therein, an adjustable blade member rotatably mounted on said hub structure and so constructed and arranged as to normally tend'to turn toward an increased pitch position during operation of said propeller, a collar confined within said hub structure and shiftably mounted on said sleeve, means for articulating the shifting movement of said collar and the rotative movement of. said blade, and a coil spring surrounding said sleeve and bearing between said collar and said hub structure for urging said blade toward a decreased pitch position.

21. A propeller including a hub structure having a propeller shaft receiving sleeve, an adjust able blade member rotatably mounted on said hub structure having its mass asymmetrically distributed with respect to its axis and being so constructed and arranged as to normally tend to turn toward an increased pitch position during operation of said propeller, said blade member including a flange on its root end portion having a recess therein, a collar shiftably mounted on said sleeve, a lever pivotally mounted on said hub structure having one end pivotally connected with said collar and its other end pivotally engaged in said recess, anda spring coacting between said collar and said hub structure for urging blade member toward a decreased pitch position.

22. A propeller including a hub structure having a propeller shaft receiving sleeve provided with a cylindrical outer peripheral portion and 5 I anadjacent shoulder, a blade member journaled in said hub structure having its mass asymmetrically distributed with respect to its rotative axis and being so constructed and arranged as to normally tend to turn toward an increased pitch position, a collar shiftably mounted on said sleeve and engageable with saidshoulder, means for articulating the shifting movements of said sleeve and the rotative movement of said blade member, and a resilient element bearing between said hub structure and said collar yieldably urging the latter against said shoulder to establish theminimum pitch of said blade.

23. A propeller including a hub structure having a propeller shaft receiving sleeve provided with a cylindrical outer peripheral portion and an adjacent shoulder, a blade member journaled in said hub structure having its mass asymmetrically distributed with respect to its rotative axis and being so constructed and arranged as to normally tend to turn toward an increased pitch position,

a counterbored collar shiftably mounted on said sleeve having one bore of larger diameter than the latter, means for articulating the shifting movements of said collar and the rotative movements of said blade member, and a coil spring concentric with said sleeve and extending into the larger bore of said collar forurging said blade member toward a decreased pitch position.

24. A propeller including a hub structure having a propeller shaft receiving sleeve. disposed therein, a hollow adjustable blade rotatably mounted in said hub having a thickened wall so constructed and arranged as to urge said blade toward an increased pitch position during operation of said propeller, said blade having a recess in its root end portion, a shit table member slidably mounted on said hub structure, means receivable in said'recess and coacting with said shiftable member for articulating the respective movements of saidmember and said blade, and resilient means bearing between said hub structure and said shiftable member for urging said blade toward a decreased pitch position.

JoHiI SQUIRES. 5o 

